1. Field of the Invention
The present invention relates to a device for lateral environment detection of a motor vehicle with a plurality of environmental sensors, which provide information for a parking support device and a door protection device. Further, the invention relates to a method for the simultaneous operation of a parking support device, which performs a parking space detection, and a door protection device for collision protection when opening at least one side door of a motor vehicle.
2. Description of the Background Art
Many devices that perform an environment detection are known from the conventional art. Normally, environment detection is performed with environmental sensors, operating according to a so-called pulse echo measuring method. An environmental sensor sends out a transmit pulse, for example, an ultrasonic pulse or an electromagnetic transmit pulse, which is reflected back from objects in the environment at least partially to the environmental sensor and is detected by said sensor as an echo pulse. A conclusion on the distance to the object is made from a time interval that passes between the sending of the transmit pulse and the receiving of the echo pulse, if the propagation speed of the sent transmit pulse is also known. Objects in the environment can be localized from a measurement data fusion via a fusion of a number of measurement results from different environmental sensors or of measurement results determined at different positions by the same environmental sensor.
In this case, the various vehicle systems that need environmental information have different requirements. A parking support device, for example, while the vehicle drives by a parking spot, would like to detect the entire lateral environment transverse to the direction of travel up to a distance of 5 m as accurately as possible. In contrast, it is sufficient for a door protection device to measure the environment in the area of a door at the distance of about 1 m, in order to be able to reliably indicate a collision risk if the door is opened and/or to actively prevent a collision. It is also important for a door protection device to detect the lateral environment even at a still low driving speed, because a measuring area covered by an environmental sensor usually cannot cover the entire pivot area of a door, in which a collision with objects can occur.
In order to enable as precise an environment detection as possible, it is desirable to possibly operate a plurality of measurement sensors simultaneously and to perform measurements with the greatest possible repeat rate.
Moreover, it is desirable for cost reasons to use as few different functional components as possible in a motor vehicle. Thus, preferably so-called equivalent parts, which are made identical, are used as functional components for a specific function. Thus, an identical part can be used at each installation location. This facilitates spare parts logistics and the replaceability of the functional components, for example. As part of fault diagnosis, functional components installed at different installation locations can be exchanged among one another in order to be able to differentiate between a defectiveness of the component and a fault in the subassembly controlling the component.
A fundamental problem in environmental sensors operating according to the pulse echo method, as do ultrasonic or radar sensors, for example, is that a transmit pulse sent by an environmental sensor generates echo pulses, which are detected not only by the environmental sensor sending the transmit pulse but also by other environmental sensors whose measuring area overlaps with a measuring area of the environmental sensor sending the transmit pulse. If it is not possible for a received echo pulse to determine the environmental sensor that has sent the associated transmit pulse, generally neither a signal transit time nor a signal path can be determined.
DE 198 39 942 A1, which corresponds to U.S. Pat. No. 6,215,415, discloses a parking aid using radar sensors, which send out transmission signals with different carrier frequencies, so that the frequencies of the received echo pulses differ from one another and assignment of the echo pulse to the individual radar sensors is possible.
DE 10 2009 053 473 A1 discloses a driver assistance device and a method for detecting an object by means of a sensor operating according to the echo transit time principle. A transmit signal with a predetermined amplitude is sent by the sensor at a transmission time. A receive signal is received by the sensor at a later receive time. The receive signal is evaluated with respect to a signal strength of the received echo pulse as to whether the echo pulse intensity is above a bottom threshold and below a top threshold. Only when this is the case is an echo pulse classified as a true echo pulse. The threshold values are dependent on the time that has passed between the sending of the transmit pulse and the time of receiving the echo pulse. The upper and lower thresholds decrease with an increasing time interval between the transmission time and the receive time. It is thereby taken into account that a signal attenuation generally occurs, the longer the signal path covered by the transmit pulse and echo pulse. If the intensity of the echo pulse is below the bottom threshold or above the top threshold, it is assumed that this is an interference pulse.
DE 10 2010 015 077 A1 discloses a method for detecting an object and a driver assistance device of a vehicle. In the described method, an ultrasonic sensor is operated in successive measurements such that the radiation characteristics of the transmit pulse are different in the successive measurements. The evaluation of the two successive measurements should also enable an angle determination to an object, in addition to a distance determination. Different radiation characteristics are achieved in an embodiment in that the ultrasonic sensor is operated at a first mechanical resonance frequency and is operated in the subsequent second measurement at a higher mechanical resonance frequency. If the ultrasonic sensor is operated at the higher mechanical resonance frequency, the ultrasonic pulse is radiated in a smaller solid angle range. In both cases, the ultrasonic sensor is operated within the ultrasonic sensor resonance range.
EP 2 127 966 A1 concerns the problem that during operation of a plurality of ultrasonic sensors in the interior of a vehicle, for example, a bus, undesirable beats can occur, if not all environmental sensors are operated at the same transmit frequency. By adjustment of the transmit frequencies, when these are not identical, a resulting beat frequency can be adjusted such that it lies outside a predetermined frequency range.
The mutual influencing of the environmental sensors is not resolved satisfactorily, when these are operated simultaneously with spatially overlapping measuring areas.